Bottom-up and top-down signaling of IL-6 with and without habituation?

Interleukin-6-mediated signaling in adrenal medullary chromaffin cells

The pro-inflammatory cytokines, tumor necrosis factor-α, and interleukin-1β/α modulate catecholamine secretion, and long-term gene regulation, in chromaffin cells of the adrenal medulla. Since interleukin-6 (IL6) also plays a key integrative role during inflammation, we have examined its ability to affect both tyrosine hydroxylase activity and adrenomedullary gene transcription in cultured bovine chromaffin cells. IL6 caused acute tyrosine/threonine phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), and serine/tyrosine phosphorylation of signal transducer and activator of transcription 3 (STAT3). Consistent with ERK1/2 activation, IL6 rapidly increased tyrosine hydroxylase phosphorylation (serine-31) and activity, as well as up-regulated genes, encoding secreted proteins including galanin, vasoactive intestinal peptide, gastrin-releasing peptide, and parathyroid hormone-like hormone. The effects of IL6 on the entire bovine chromaffin cell transcriptome were compared to those generated by G-protein-coupled receptor (GPCR) agonists (histamine and pituitary adenylate cyclase-activating polypeptide) and the cytokine receptor agonists (interferon-α and tumor necrosis factor-α). Of 90 genes up-regulated by IL6, only 16 are known targets of IL6 in the immune system. Those remaining likely represent a combination of novel IL6/STAT3 targets, ERK1/2 targets and, potentially, IL6-dependent genes activated by IL6-induced transcription factors, such as hypoxia-inducible factor 1α. Notably, genes induced by IL6 include both neuroendocrine-specific genes activated by GPCR agonists, and transcripts also activated by the cytokines. These results suggest an integrative role for IL6 in the fine-tuning of the chromaffin cell response to a wide range of physiological and paraphysiological stressors, particularly when immune and endocrine stimuli converge.

THE SHORT-TERM IMPACT OF UNCONDITIONAL CASH TRANSFERS TO THE POOR: EXPERIMENTAL EVIDENCE FROM KENYA

We use a randomized controlled trial to study the response of poor households in rural Kenya to unconditional cash transfers from the NGO GiveDirectly. The transfers differ from other programs in that they are explicitly unconditional, large, and concentrated in time. We randomized at both the village and household levels; furthermore, within the treatment group, we randomized recipient gender (wife versus husband), transfer timing (lump-sum transfer versus monthly installments), and transfer magnitude (US$404 PPP versus US$1,525 PPP). We find a strong consumption response to transfers, with an increase in household monthly consumption from $158 PPP to $193 PPP nine months after the transfer began. Transfer recipients experience large increases in psychological well-being. We find no overall effect on levels of the stress hormone cortisol, although there are differences across some subgroups. Monthly transfers are more likely than lump-sum transfers to improve food security, whereas lump-sum transfers are more likely to be spent on durables, suggesting that households face savings and credit constraints. Together, these results suggest that unconditional cash transfers have significant impacts on economic outcomes and psychological well-being.

Blunted IL-6 and IL-10 response to maximal aerobic exercise in patients with traumatic brain injury

INTRODUCTION

In healthy individuals, strenuous exercise typically results in a transient increase in the inflammatory cytokine, interleukin-6 (IL-6). This increase in IL-6 is reported to have pleiotropic effects including increased glucose uptake, increased fat oxidation, and anti-inflammatory actions.

PURPOSE

The purpose of this study was to determine if patients with a traumatic brain injury (TBI) have a differential cytokine response to exercise compared to healthy control subjects (CON).

METHODS

Eight patients with a TBI and eight age- and sex-matched controls completed an exercise test to volitional exhaustion. Metabolic data were collected continuously, and blood was collected at baseline, immediately post-exercise, and every 10 min for an hour post-exercise. Serum was analyzed for IL-6, tumor necrosis factor-alpha, interleukin-10 (IL-10), and cortisol.

RESULTS

Peak oxygen consumption (CON 33 ± 2 ml kg(-1) min(-1); TBI 29 ± 2 ml kg(-1) min(-1)) and respiratory exchange ratio during exercise were equivalent between groups. There were no baseline differences between groups for cytokine or cortisol concentrations. Exercise did not increase IL-6 in TBI, whereas IL-6 was elevated from baseline in CON at 0, 40, and 50 min post-exercise (p < 0.05). IL-10 and cortisol increased from baseline in CON at 40 min post-exercise (p < 0.05).

CONCLUSIONS

These data indicate that patients recovering from TBI have blunted IL-6, IL-10, and cortisol responses following a peak exercise test compared to non-TBI controls. This lack of an exercise response may represent impaired hypothalamic-pituitary-adrenal axis function.

Association of elevated cytokines with childhood adversity in a sample of healthy adults

OBJECTIVE

Childhood trauma has been associated adult stress-related disorders. However, little is known about physiologic alterations in adults with a history of early life trauma that do not have current psychiatric or medical diagnoses. In this study, the relationships between childhood adversity and cytokine and C-reactive protein (CRP) levels in healthy adults were examined.

METHOD

Participants included men (n = 18) and women (n = 20) who did not meet DSM-IV criteria for Axis I psychiatric disorders or any major medical illness. Cytokine and CRP levels were obtained from baseline blood samples. Subjects completed the Early Trauma Inventory Self Report (ETI-SR). The primary outcomes included serum interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1β (IL1-β), and CRP levels. In addition, the mean numbers of traumatic experiences (sexual, physical, emotional, general, and the summed total) were measured.

RESULTS

Significant positive associations were found between the total ETI score and IL-6 (p = 0.05), IL1-β (p < 0.05), and TNF-α (p = 0.01). Significant positive correlations were found between the number of general traumas and IL1-β (p < 0.05), TNF-α (p < 0.05), and IL-6 (p < 0.01). Neither the total number of traumas nor any of the trauma subscales were significantly associated with CRP levels.

CONCLUSIONS

The positive association between childhood trauma and basal cytokine levels supports the extant literature demonstrating the long-term impact of childhood trauma and stress on homeostatic systems. Importantly, this association was found in healthy adults, suggesting that these alterations may precede the development of significant stress-related psychiatric disorder or disease.

Cytokine interactions with adrenal medullary chromaffin cells

It is generally accepted that a bi-directional or reciprocal interaction occurs between the immune and neuroendocrine systems, and that this relationship is important for the appropriate physiological functioning of both systems. Similarly, an imbalance in this relationship may contribute to a number of pathologies, most notably those relating to stress. The aim of this article is to consider the interaction of cytokines with the adrenal medulla, a potentially important player in this relationship. The chromaffin cells of the adrenal medulla release catecholamines and a range of biologically active peptides in response to a wide variety of stress-related signals. A growing body of evidence indicates that this stress response is influenced by, and in turn has influence upon, immune signalling. This brief review will focus primarily on the best-described adrenal medullary active cytokines, namely interferon-α, interleukin-6, interleukin-1α/β and tumour necrosis factor-α. In each case, three key issues will be addressed: the physiologically relevant source of the cytokine; the intracellular signalling events arising from activation of its receptor and finally the cellular consequences of such activation in terms of modulation of gene expression and the secretory output of the chromaffin cells.

Does thalidomide have an analgesic effect? Current status and future directions

Dramatic relief of pain and life-altering changes in quality of life in some patients treated with immunomodulators such as thalidomide compel us to look more closely at unconventional mechanisms that may be involved in propagation of persistent pain. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, and IL-10 are the cytokines with the most evidence in pain modulation. TNF-alpha and IL-1beta seem to initiate neuropathic pain, IL-6 maintains such pain, and IL-10 inhibits this persistent pain. Thalidomide was found to be effective in animal models by inhibiting TNF-alpha production. Several case reports and case series in humans have demonstrated mixed results, with some patients having dramatic responses, especially in chronic intractable conditions such as complex regional pain syndrome. Thalidomide may be an alternative for some patients with intractable pain. However, use of thalidomide is limited by its neurotoxic and teratogenic effects. Newer analogues may significantly improve the risk/benefit of using such immunomodulators.